Filter dyes are widely used in photographic elements. Filter dyes may be located in several locations in an element. They may be in a radiation-sensitive layer, an overcoat layer, in a layer adjacent to the radiation-sensitive layer, in an interlayer of a multilayer element, in an undercoat layer adjacent to the support or in a backing layer on the side of the support opposite the radiation-sensitive layer.
When incorporated directly in the radiation-sensitive layer they can function to improve sharpness by absorbing light scattered from one silver halide grain to another. Such dyes are referred to as absorber dyes. Filter dyes also function to retard the sensitivity of one light sensitive layer relative to another in a multilayer element. By absorbing some of the exposing radiation the filter dye aids in balancing the sensitivities of all the light sensitive layers.
Filter dyes that function primarily to absorb unwanted radiation due to reflection or refraction from layer interfaces, the layer-support interface, and particularly from the back side of the support, are referred to as antihalation dyes. The layers that contain them are referred to as antihalation layers.
There are other places and purposes for filter dyes and filter layers. For example, a filter layer may be used in or near the overcoat layer to protect the light sensitive layer against radiation from certain spectral regions. In multilayer films where there may be two or more light sensitive layers, it is sometimes necessary to have filter dye interlayers. In duplitized.RTM. materials, such as X-ray films, filter layers are used to reduce crossover exposure of the light sensitive layers. Elimination of crossover exposure is an ideal that is highly desirable but has not yet been fully attained.
A number of problems are associated with filter dyes and filter layers. It is very important that the dyes remain in the layer and not wander or diffuse into the adjacent layers. This often necessitates the presence of a mordant to hold the dye in the layer. It is equally important for the dyes to be completely decolorized and/or removed from the element, usually during processing, after they have performed their function. Dye stability, especially under high temperature and high humidity incubation is also important.
In some photographic elements, it is desirable to absorb unwanted radiation across the entire visible spectrum. In such elements it is not unusual to use up to five filter dyes in a single filter layer to accomplish this desirable objective. Clearly it would be an improvement to reduce the number of filter dyes used in the layers of such elements.
U.S. Pat. No. 3,560,214 discloses dyes comprising a carboxyl and phenyl substituted pyrazoline nucleus linked through a methine group to a dialkylaminophenyl group. However these dyes, according to the patent and our own experiments, are migratory.
It is an objective of this invention to provide filter dyes for photographic elements which meet the foregoing requirements for filter dyes, do not cause post process dye stain or migrate from layer to layer and reduce the number of filter dyes needed in a filter layer.